package c1701;

import java.util.Scanner;

public class M {
    public static StringBuffer An(int n) {
        if (n == 1) {
            return new StringBuffer("A");
        } else {
            StringBuffer buffer = An(n - 1);
            buffer.append((char) (n + 64));
            buffer.append(buffer.toString());
            buffer.deleteCharAt(buffer.length() - 1);
            return buffer;
        }
    }

    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        System.out.println(An(input.nextInt()));
    }
}